Physics in Your World

If light bends at the air-glass surface, then what good is the glass inside the lens? This question led to the development of the Fresnel lens--the photo above (hi-res version) shows an example, in a lighthouse. To learn how these lenses work, visit Fresnel Lens from HyperPhysics.

Physics at Home

For a remarkable optical illusion, see Cheshire Cat from the Exploratorium. By watching a person's face with one eye and a wall--reflected in a small mirror--with the other, you can make most of the features of the face disappear, often leaving only the eyes or mouth. Try it!

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From Physics Research

In the photograph above (hi-res version), each pair of spirals that originate from the same point is the track of an electron-positron pair. The positron is the antiparticle of the electron--it has the same mass as the electron, but the opposite charge. These pairs are formed when a photon--which leaves no track--changes into particles with mass. For more information about this photo, see the "antielectron (positron)" section of the "Gallery of Bubble Chamber (BC) Pictures" at CERN's Introduction to the BC Site and "Special pictures and their interpretation: Photons, electrons and positrons" at CERN's Archived Bubble Chamber Teaching Materials.